The present invention relates to the fabrication of semiconductor integrated circuits, and in particular, to cleaning compositions and methods for cleaning surfaces during fabrication.
In the manufacture of integrated circuits, interconnects are used to couple active and passive devices together and to couple together conductive lines formed on different layers of the integrated circuits. To keep the resistivity in the interconnects low, interconnects are generally fabricated from good conductors, such as aluminum, copper, or alloys of aluminum or copper. Keeping the resistivity of the interconnects low decreases the heat generated in the interconnects, which permits the fabrication of higher density circuits.
Unfortunately, even for interconnects having a low resistivity, the interface between the interconnect and an active or passive device or the interface between the interconnect and a conductive line may have a high resistivity. High resistivity at an interconnect interface is often caused by an unclean surface at the interface. Preclean procedures and preclean chemicals, such as phosphoric acid, and hydrofluoric acid, are used to prepare semiconductor surfaces at interconnect interface sites. Unfortunately, these chemicals contain strong (i.e., concentrated and not dilute) organic solvents, which require special hazardous waste disposal techniques.
For example, U.S. patent application Ser. No. 08/808,014 (which is assigned to the same assignee of the present invention) discloses suitable compositions useful as cleaning compositions in integrated circuits semiconductor fabrication. The compositions include water, phosphoric acid, and acetic acid. The compositions are successful in reducing surface aluminum fluorides but require special hazardous waste disposal techniques. Preclean procedures and chemicals are also used to prepare metal surfaces, such as aluminum or copper surfaces, at interconnect interface sites. Unfortunately, the common contaminants, such as residual organic and metallic impurities are difficult to remove, and the conventional cleaning compositions also require special hazardous waste disposal techniques.
For these and other reasons there is a need for the present invention.
The present invention provides a composition useful as a cleaning composition in semiconductor integrated circuit fabrication. The composition of the present invention provides improved solvation of metallized polymers and organic polymers over previously used cleaning compositions, such as standard phosphoric acid cleans. The composition is advantageous as compared with previously used strong (i.e., concentrated and not dilute) organic solvent cleans because the composition does not require special hazardous waste disposal. In addition, the composition of the present invention sufficiently reduces the overall volume of etch residue remaining post-clean.
In one embodiment, the present invention provides a composition useful as a cleaning composition in semiconductor integrated circuit fabrication. The composition includes water, phosphoric acid, and an organic acid. The organic acid is ascorbic acid or is an organic acid having two or more carboxylic acid groups. In one specific embodiment of the invention, the organic acid is citric acid, ascorbic acid, or a combination thereof.
In an alternative embodiment, the present invention provides another composition useful as a cleaning composition in semiconductor integrated circuit fabrication. The composition includes about 40 wt. % to about 85 wt. % water, about 0.01 wt. % to about 10 wt. % phosphoric acid, and about 10 wt. % to about 60 wt. % of an organic acid, wherein the organic acid is ascorbic acid or is an organic acid having two or more carboxylic acid groups; wherein the composition is useful as a cleaning composition in semiconductor integrated circuit fabrication. In one specific embodiment of the invention, the organic acid is citric acid, ascorbic acid, or a combination thereof.
In an alternative embodiment, the present invention provides another composition useful as a cleaning composition in semiconductor integrated circuit fabrication. The composition includes about 40 wt. % to about 85 wt. % water, about 0.01 wt. % to about 10 wt. % phosphoric acid, and about 10 wt. % to about 60 wt. % of ascorbic acid, citric acid, or a combination thereof; wherein the composition is useful as a cleaning composition in semiconductor integrated circuit fabrication.
In an alternative embodiment, the present invention provides a cleaning method in a semiconductor fabrication process. The method includes providing a composition of the present invention and exposing a surface to the composition.
In an alternative embodiment, the present invention provides a method of fabricating an interconnect structure. The method includes patterning a conductive layer and cleaning the conductive layer using a composition of the present invention.
In an alternative embodiment, the present invention provides a method of fabricating a multilevel interconnect structure. The method includes providing an insulating layer over a first metal layer; defining a via in the insulating layer, resulting in residue on an exposed portion of the first metal layer; and removing the residue using a composition of the present invention.
In an alternative embodiment, the present invention provides a method of fabricating a multilevel interconnect structure. The method includes patterning a first metal layer over a contact hole using a photoresist and etchant; forming an insulating layer over the first metal layer; defining a via in the insulating layer over the first metal layer, resulting in organic residue on at least a portion of the via; and removing the organic residue on the via using a composition of the present invention.